High frequency operation of JTL ring oscillator with a passive transmission line

We have designed ring oscillators to test rapid single nux quantum (RSFQ) c ircuits with passive transmission lines at high frequencies, To reduce the width of the transmission line, design methods for increasing the character istic impedance of the transmission line have been investigated and then we designed a Li-stage of Josephson transmission line (JTL) receiver which ca n transform the impedance from 1 to 4 Omega by changing the critical curren t and the inductance. The receiver, driver, and micro-strip line were inser ted in a ring oscillator. The ring oscillator fabricated with the Nb/AlOx/N b junction process was successfully operated at frequencies ranging from 6 to 10 GHz for line lengths of 0.6, 3, 6, and 9 mm, The usefulness of the im pedance transformation was then confirmed experimentally. A propagation del ay per unit length of 8.4 ps/mm was also obtained.